Which U.S. market regulator introduced the first nationwide circuit breakers after the 1987 crash?

The U.S. Securities and Exchange Commission introduced nationwide circuit breakers after the 1987 crash.

The October 1987 collapse exposed how quickly automated and coordinated selling could overwhelm market systems. In response, the SEC approved market-wide trading halts, commonly called circuit breakers, that could pause trading after specified declines.

The first system used fixed point thresholds based on the Dow Jones Industrial Average. It was later revised as index levels changed, and modern rules use percentage declines in the S&P 500. The purpose is to interrupt extreme downward momentum and allow investors and exchanges to review information.

Circuit breakers do not prevent losses or guarantee a recovery. They are temporary pauses, not price supports. They are also distinct from exchange-specific rules that may halt one stock because of unusual activity. The post-1987 reforms created a nationwide framework for broad market declines.